The present invention relates to a fluid circulation conduit. It finds a particular application in heating systems installed on household equipment. This includes in particular machines for preparing beverages by the infusion of a product such as ground coffee or chopped tea leaves, or by the dissolving of a product, especially in granulated form. A preferred application is to be found in espresso-type coffee machines.
In this latter indicative field of use, the fluid, in this case water, has to be heated to levels which ensure maximum extraction of the aromatic substances found in ground coffee. Devices called boilers are provided for this purpose. They have in common a circuit through which the heated water transits and means for heating the water, generally an electrical heating resistance. As an example, the water temperature of 20° C. at the intake is increased to a temperature at the outlet of between 70 and 100° C.
One of the shortcomings of conventional boilers is the time that is required to increase the temperature of the water circulating through the circuit. Indeed, conventional boilers are large consumers of electricity, especially when used on household appliances that are repeatedly started and stopped. This is particularly true in the field of coffee machines that are stopped and started several times in the course of one day. In addition to their high energy consumption, conventional boilers are slow to heat up, leading to a waiting time that a user may find annoying.
More sophisticated boilers with faster means of heating have recently been proposed. These are equipped with means that ensure that the temperature increase generally takes place in less than 10 seconds. In particular, techniques using thick film screen-printed resistances ensure a quasi immediate response by the boiler heating means. However, technical limitations have been observed, especially regarding temperature setting.
Thus, a need has arisen to improve the heating capacity of the fluid transiting through a conduit so as to obtain the best heating time/temperature performance.